diff --git a/Cocoa/Document.m b/Cocoa/Document.m
index 1dbefaf..24482c3 100644
--- a/Cocoa/Document.m
+++ b/Cocoa/Document.m
@@ -11,7 +11,8 @@
      reasonable alternative to this. */
     unsigned long pendingLogLines;
     bool tooMuchLogs;
-    
+    bool fullScreen;
+
     NSString *lastConsoleInput;
 }
 
@@ -262,8 +263,21 @@ static uint32_t rgbEncode(GB_gameboy_t *gb, uint8_t r, uint8_t g, uint8_t b)
 }
 
 
+- (void) windowWillEnterFullScreen:(NSNotification *)notification
+{
+    fullScreen = true;
+}
+
+- (void) windowWillExitFullScreen:(NSNotification *)notification
+{
+    fullScreen = false;
+}
+
 - (NSRect)windowWillUseStandardFrame:(NSWindow *)window defaultFrame:(NSRect)newFrame
 {
+    if (fullScreen) {
+        return newFrame;
+    }
     NSRect rect = window.contentView.frame;
 
     int titlebarSize = window.contentView.superview.frame.size.height - rect.size.height;
diff --git a/Cocoa/Document.xib b/Cocoa/Document.xib
index 754e92f..472f71f 100644
--- a/Cocoa/Document.xib
+++ b/Cocoa/Document.xib
@@ -18,6 +18,7 @@
         <customObject id="-3" userLabel="Application" customClass="NSObject"/>
         <window title="Window" allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" releasedWhenClosed="NO" visibleAtLaunch="NO" animationBehavior="default" id="xOd-HO-29H" userLabel="Window">
             <windowStyleMask key="styleMask" titled="YES" closable="YES" miniaturizable="YES" resizable="YES"/>
+            <windowCollectionBehavior key="collectionBehavior" fullScreenPrimary="YES"/>
             <windowPositionMask key="initialPositionMask" leftStrut="YES" rightStrut="YES" topStrut="YES" bottomStrut="YES"/>
             <rect key="contentRect" x="133" y="235" width="160" height="144"/>
             <rect key="screenRect" x="0.0" y="0.0" width="2560" height="1417"/>
diff --git a/Cocoa/Preferences.xib b/Cocoa/Preferences.xib
index af4b38e..43b27b4 100644
--- a/Cocoa/Preferences.xib
+++ b/Cocoa/Preferences.xib
@@ -13,6 +13,7 @@
         <customObject id="-3" userLabel="Application" customClass="NSObject"/>
         <window title="Preferences" allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" oneShot="NO" releasedWhenClosed="NO" animationBehavior="default" id="QvC-M9-y7g" customClass="GBPreferencesWindow">
             <windowStyleMask key="styleMask" titled="YES" closable="YES"/>
+            <windowCollectionBehavior key="collectionBehavior" fullScreenAuxiliary="YES"/>
             <windowPositionMask key="initialPositionMask" leftStrut="YES" rightStrut="YES" topStrut="YES" bottomStrut="YES"/>
             <rect key="contentRect" x="196" y="240" width="292" height="292"/>
             <rect key="screenRect" x="0.0" y="0.0" width="2560" height="1417"/>